Failure Mechanism Of Silicon Carbide Capacitive Pressure Sensor Under Temperature And Pressure Conditions

With the development of the third-generation wide-bandgap semiconductor SiC materials and miniature sensor technology,the application fields of SiC capacitive pressure sensors have become more extensive,and the environmental stresses involved have become more complex and harsh.At present,domestic and foreign research focuses on the realization of the finished product process of SiC capacitive pressure sensors,the preparation of key structure samples,the construction of simulation models,the optimization of output characteristics,the single static environmental stress,the static comprehensive stress and the frequency domain comprehensive stress simulation.There are few studies on the influence of SiC capacitive pressure sensors on long-term high-temperature environmental stress,large-scale pressure fatigue environmental stress and comprehensive environmental stress,especially the lack of discussion on high-temperature creep phenomenon in the study of long-term high-temperature environmental stress.Moreover,the failure mechanism of the sensor under the coupling of environmental stress is not clear enough.Therefore,in response to the above problems,this article is based on the ANSYS finite element platform,from the three aspects of temperature,pressure and comprehensive environmental stress SiC capacitive pressure sensor finite element simulation,combined with the sensor-related sample preparation test data analysis,research in temperature,pressure,etc.Reliability and failure mechanism of SiC capacitive pressure sensor under environmental stress.In this paper,the transient thermal-structure coupling simulation of the SiC capacitive pressure sensor under the long-term thermal environment for the high temperature environment is carried out,and the simulation process of the temperature field,elastic force field and high temperature creep force field coupling is formed.The convergent temperature field is obtained by densifying the grid and optimizing the thermal load;according to the test results,the high-temperature creep parameters are calibrated and optimized,the high-temperature creep constitutive model and parameters of the SiOO₂ film are imported into the structure field,and the load transfer method is adopted.The temperature field obtained by the solution is imported into the structure field by means of equidistant compression for residual stress analysis.It is calculated that the maximum residual stress of the SiOO₂layer of the sensor package structure after the end of high temperature and constant temperature for 1 hour and 20 high and low temperature impacts are 174.80MPa and 115.83MPa,respectively,and the cumulative residual strain is 0.00725?m/?m and 0.00538?m/?m,respectively.The drift amounts are 0.1103%and 0.0274%respectively.Through temperature environment stress simulation analysis,the accumulation of residual stress and strain over time and space after a long-term and rapidly changing high-temperature environment can be obtained,especially the stress distribution of the SiOO₂ layer of the key structure.Combining the stress and strain of the chip structure sample and the SEM cross-section test analysis results,starting from the failure of mechanical and electrical characteristics,the failure mode and mechanism of the SiC capacitive pressure sensor under the temperature environment are investigated.Secondly,using the ANSYS transient structure module,the pressure fatigue simulation analysis based on the chip and the package structure was carried out respectively,and the mechanism of the rapid change of a large number of pressure cyclic loads on the SiC capacitive pressure sensor was studied.Through simulation,the structure response during different pressure cycles is obtained,and the accumulation of sensor stress and deformation with the number of cycles is obtained.The maximum residual stress of the chip and package structure after fatigue are 1607MPa and 445.43MPa,and the maximum strain is 0.0249?m/?m and 0.00895?m/?m,by extracting the deformation to calculate the capacitance,the zero capacitance drift of the chip and package model after pressure cycling is 0.8526%and 0.2215%,respectively.In addition,linear epitaxy of the stress-time curve,combined with the yield strength of the SiOO₂ film,predicts the number of critical failure pressure cycles,that is,the theoretical limit of the chip/package model pressure fatigue is 14454/26258 times.The adaptability and failure mechanism of SiC capacitive pressure sensor under pressure fatigue environment are analyzed from both mechanical and electrical failure degradation.Finally,based on the ANSYS Multiphysics multi-physics coupling module,a time-domain integrated environmental stress simulation analysis of the SiC capacitive pressure sensor is carried out.In terms of the two stresses,the coupled simulation of temperature-pressure and temperature-impact was carried out.On this basis,the three-stress coupling simulation of temperature,pressure and shock was also carried out.The temperature-structure field adopts an indirect coupling method,and the Pressure and shock use direct coupling method.The residual stresses of the SiOO₂layer are174.97MPa,513.66MPa,and 552.05MPa,respectively.The zero point changes of the capacitance output characteristics after the action of temperature-pressure,temperature-impact and three comprehensive stresses are 0.08149%,0.1132%,and0.1323%,respectively.Analyze the relationship between residual stress,capacitance zero drift and different environmental stresses and structural materials,and finally obtain the weak material and position of the SiC capacitive pressure sensor at high temperature,pressure,impact,etc.separately and after the combined action,and give the comprehensive environmental stress transmitter environmental adaptability and potential failure laws.